\def{integer n=randint(2..4)}
\def{text liste=sin(2*pi*sss)/2, cos(2*pi*sss)+0.5
0.5+cos(2*pi*sss)*cos(2*pi*sss),0.5+cos(2*pi*sss)*sin(2*pi*sss)
0.3+(1+cos(2*pi*sss))*cos(2*pi*sss)/2,(1+cos(2*pi*sss))*sin(2*pi*sss)
1+sin(2*pi*sss)^3/2,1+cos(2*pi*sss)^3/2
sin(2*pi*sss)^3/2,1+3*cos(2*pi*sss)^3/4
0.5+4*sss*(1-sss),7*sss^2*(1-sss)
-0.5+4*sss*(1-sss)^2,7*sss^2*(1-sss)
}
\def{text courbe=randrow(\liste)}
\def{text x=\courbe[1]}
\def{text y=\courbe[2]}
\def{text xt=wims(replace internal sss by t in \x)}
\def{text yt=wims(replace internal sss by t in \y)}
\def{text x=wims(replace internal sss by s in \x)}
\def{text y=wims(replace internal sss by s in \y)}
\def{text ab=sqrt((4-(\x)^2-(\y)^2)/((\x)^2+(\y)^2))/2}
\def{text a=(\x)/2+(\y)*(\ab)}
\def{text b=(\y)/2-(\x)*(\ab)}
<table><tr><td>
\reload{<img src="gifs/doc/etoile.gif" alt="rechargez" width="20" height="20">} Voici un exemple de courbe parcourue par un planimtre.
Vous pouvez en changer en cliquant sur l'toile.
</td><td align="center">
<center>
\draw{400,400}{
animate 50,0.1,0
xrange -2,2
yrange -2,2
trange 0,2*pi
plot grey, cos(t),sin(t)
linewidth 3
disk 0,0,10, blue
disk \a,\b,8, blue
disk \x,\y,8, red
lines green, 0,0,\a,\b,\x,\y
line (2*(\a)+(\x))/3-(\y-(\b))/10,(2*(\b)+(\y))/3+(\x-(\a))/10,(2*(\a)+(\x))/3+(\y-(\b))/10,(2*(\b)+(\y))/3-(\x-(\a))/10,red
linewidth 1
arrow \x,\y,\x-(\y-(\b))/2,\y+(\x-(\a))/2, 10,black
trange 0,1
plot red, \xt,\yt
plot blue ,cos(2*pi*t),sin(2*pi*t)
}
</td></tr>
</table>